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Ground worker
Back-Drop Benching Bit-Mac
Blinding Brushed Concrete DPM
Formation Hepsleve Plastic
Salt-glazed Spoil Sub-base
Tamped Concrete    
Where underground drain runs have to change level to go lower, it is not possible to increase the slope downwards beyond certain limits as anything other than clear liquid would be left behind. The way to overcome this is to construct a manhole where the drain comes in at the top and the sewage then free falls down a vertical pipe inside the manhole to the new lower level. The advantage to this method is that the manhole is easily accessible for rodding out blockages. The manhole is called the backdrop.
The channel at the bottom of the manhole is finished with smoothed mortar render to form a self-cleaning slope. This is called benching. Sometimes the benching may break up causing drain to block.
Bitumen macadam coated aggregate, which is laid hot for road and drive surfaces. It is generally laid as a two-layer make up with the base course using 20-38mm stone and the wearing course 5-12mm of stone. Dense bitmac (dbm) refers to graded stone where fine stone is mixed in to fill the gaps and add strength. This is generally used for roads or heavily trafficked drives.
Sand topping approximately 30-50mm laid on the surface of the sub-base to prevent the toppings from running into the sub-base. The blinding also allows the toppings to move independently from the sub-base.
Concrete surface that has been smoothed then finished with a lightly dragged broom to provide grip. This is often seen on petrol garage forecourts.
Damp proof membrane, used immediately below the concrete ground floor slab to prevent rising damp. This is also sometimes used on top of the blinding on concrete drives as a slip membrane to ensure no binding between the layers.
The deepest point in an excavation for a drive or patio, which is leveled and smoothed prior to laying the sub-base.
A trade name for very hard clay pipes jointed with plastic collars.
Plastic pipes are often used in domestic underground drainage, as the pipe lengths are light and long compared to clay. The disadvantage is that the pipes are not as strong and may have to be encased in concrete in certain conditions, negating any flexible qualities. In such circumstances, clay may be a better choice.
Before the super baked clay drainage pipe used today was developed, clay pipes had to be coated in a kiln-fired clear glaze to ensure a watertight smooth surface. These pipes were jointed rigidly with sand/cement and tarred hemp.
Material dug out from an excavation, which may be referred to on site as muck and muck-away for removing from site.
The coarse filling such as hardcore or crushed rock that forms a frost resistant strong base to spread and cushion the loads. This is usually at least 100mm thick.
Concrete surface compaction with long heavy board leaving shallow ridges. The ridges should be shallow to allow water to drain.
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